Cognitive therapy has been shown to be at least as effective as, if not more effective than, pharmacotherapy in the treatment of non-bipolar outpatient depressives and, perhaps, more effective in terms of preventing subsequent relapse. To date, no studies have examined the efficacy of combining cognitive therapy with pharmacotherapy. This project consists of a main study examining the comparative efficacies of cognitive therapy, pharmacotherapy, pharmacotherapy with extended maintenance, and combined cognitive-pharmacotherapy in the treatment of primary, non-bipolar, depressed outpatients. Treatment efficacy will be evaluated in terms of response to treatment, prevention of relapse, and minimization of drop-out rates. A series of cross-lagged panel analyses and multivariate analyses will be utilized to explore 1) a variety of hypotheses regarding the mechanisms of change associated with each treatment modality (e.g., the relationships between biochemical indices, cognitive processes, and levels of syndrome depression), and 2) potential predictors of both response to treatment and maintenance of treatment gains.